The invention relates to position encoder apparatus, and more particularly, to an apparatus for generating coordinate information of an object intersecting a predefined plane.
Coordinate definition devices utilizing light beams to identify the coordinates of an object intersected by the light beams are many and varied. In one such device, a special pointer is provided whereby a light beam intersecting the pointer is reflected backwardly along its incoming path to a light detector. The time of detection can be utilized to determine the angle of the light beam with respect to a predetermined angle. However, this device requires a specially designed pointer which must be readily available. Another system utilizes a plurality of discrete detectors which provide identifiable output signals when the light beam is interrupted. By identifying the specific detector in line with the interrupted light beam, the angle of that beam with respect to a predetermined angle can be determined. However, the accuracy of these types of systems is limited by the number and resolution of the detectors being utilized. The present invention solves the above problems by utilizing a continuous optical sensor whereby the resolution of the system is only limited by the accuracy to which the time of beam interruption with respect to a reference time can be determined. Thus, no special pointer is required, only a pointer that is at least partially opaque to the beam light.